This invention relates to a closed loop transfer system and, more particularly, relates to such a system having one-piece leak proof couplers used for liquid supply and vapor recovery.
There are various arrangements in the art for providing closed loop fluid transfer. Such systems used in technologies and in situations where fluid is to be transferred from one vessel to another but where, in doing so, vapor phase components of the fluid must not be permitted to escape from the system, as into the atmosphere. Among the fluids often so transferred are solvents and other volatile organics.
A salient example is perchlorethylene (“PERC” or “perc”), also known as tetrachloroethylene, a colorless, nonflanmable liquid. It is the most common cleaning solvent used in the dry cleaning industry.
Because of the possible risks in human exposure to perchlorethylene vapors, environmental restrictions of a regulatory nature require transfer of perchlorethylene to and from dry cleaning machinery, as between such machinery and shipment or delivery vessels, in a manner as will prevent escape of perchlorethylene vapors. Perchlorethylene is also used in the textile industry and in vapor degreasing and metal cleaning operations. It is also a component in other formulations. Perchlorethylene is representative of a class of volatile organic fluids which, when transferred, should not be permitted to escape as fluid or vapor.
Any such volatile organic fluid is herein referred to for convenience as a “VOF” and, in its liquid phase, is referred to as a “VOF liquid” and in its vapor phase as “VOF vapor”.
One such system for providing closed loop fluid transfer for transfer of perchlorethylene transfers this chemical from a mobile dispensing apparatus delivery container to a device to receive the chemical, viz., a dry cleaning machine. In such an arrangement the dispensing apparatus provides a VOF liquid delivery line and a VOF return line. VOF liquid (e.g., perchlorethylene) is pumped from the delivery vessel supported by a cart, for dispensing with precise metering through the VOF liquid delivery line to a fluid-receiving device such as a dry cleaning machine. Vapor is returned to the delivery vessel through a VOF vapor return line. Both lines are preferably connected to the fluid-receiving device by a one-piece dry-disconnect coupler capable of providing both liquid flow and vapor recovery, so as ensure that there will be no leaks or fumes or vapors released when the liquid is dispensed to the machine.
It has been found that under certain flow conditions, the VOF liquid when pumped under certain undesired conditions may result in liquid being forced back into the vapor return line. The undesired conditions may result from improper installation or connection by service personnel of the line fittings to the receiving machine, inadvertent inclination of connectors, or from an imbalanced flow. In any event, the inadvertent return of liquid in the vapor return line is not desirable, as fluid will may not be efficiently received by the fluid-receiving device, or delivery of the liquid VOF may be intermittent. This may require greater filling or “charging” time, or the liquid may not be as accurately metered as desired because of errors introduced because of liquid in the vapor return line.